The Department of Housing and Urban Development (HUD) defines a chronically homeless person as an individual who is an unaccompanied adult with a disabling condition who has been homeless for a year or more, or those who have experienced at least four episodes of homelessness within three years. HUD classifies a disabling condition as a diagnosable, serious mental illness, developmental disability, chronic physical illness, substance use disorder, or disability including the co‐occurrence of two or more of these conditions.

According to the National Alliance to End Homelessness an estimated 63 percent of people who experience homelessness at any given point in time are individuals or single adults. Most enter and exit the homeless system fairly quickly. The remainder live in the homeless assistance system; in a combination of shelters, hospitals, jails, prisons; or on the streets. An overwhelming majority of single adult shelter users enter the homeless system only once or twice, staying just over a month, and do not return. Approximately 9 percent enter nearly five times a year and stay nearly two months each time. This group utilizes 18 percent of the system’s resources.

The remaining 10 percent enter the system just over twice a year and spend an average of 280 days per stay, virtually living in the system and utilizing nearly half its resources. Many of these individuals are defined by the Department of Housing and Urban Development (HUD) as chronically homeless.

Chronically homeless individuals often cycle between homelessness, hospitals, jails, and other institutional care and often have a complex medical problem, a serious mental illness like schizophrenia, and/or alcohol or drug addiction. There are approximately 123,790 chronically homeless individuals nationwide on any given night. Although chronically homelessness represents a small share of the overall homeless population, chronically homeless people use up more than 50 percent of the services.